The present invention generally relates to crosstalk noise calculation methods and storage mediums, and more particularly to a crosstalk noise calculation method for calculating a crosstalk noise of an adjacent wiring and to a computer-readable storage medium which stores a program for causing a computer to calculate the crosstalk noise using such a crosstalk noise calculation method.
When wirings to be formed on an assembling board of a computer, printed circuit board, printed wiring board and the like are designed by computer aided design (CAD), a crosstalk noise between adjacent wirings may exceed a tolerable range due to an error in the design, an error in the wiring rule or the like. For this reason, it is necessary to finally determine the wirings by checking whether or not the crosstalk noise falls within the tolerable range. The crosstalk noise between the adjacent wirings can be obtained by simulation. But in the case of the assembling board of a personal computer, for example, there are more than 1000 wirings. Further, the number of wirings is more than ten times that of the assembling board of the personal computer, that is, more than 10000, in the case of the assembling board of a work station, super computer and the like. Hence, it takes too much time to obtain the crosstalk for all of the wirings by simulation.
Accordingly, the crosstalk noise of the wiring is obtained by calculation, and the wiring is determined so that the calculated crosstalk noise falls within the tolerable range.
FIG. 1 is a diagram for explaining a conventional crosstalk noise calculation method. In FIG. 1, the ordinate indicates a peak value of the crosstalk noise, and the abscissa indicates a length of parallel wirings (hereinafter referred to as a parallel wiring length).
As may be seen from FIG. 1, the crosstalk noise is conventionally calculated using a function F by assuming that the peak value of the crosstalk noise is simply proportional to the adjacent wiring length. In the conventional assembling board and the like, the density of the wirings is relatively low, the wiring length is relatively short, and a transfer rate of a signal flowing through the wirings is relatively low. For these reasons, the crosstalk noise calculated using the function F shown in FIG. 1 was a relatively good approximation, and in addition, the calculation itself was also simple.
However, due to the increased operation speeds of CPUs and the development of high-speed memory elements, the wiring density on the assembling board and the like has recently increased, the wiring length has increased, and the transfer rate of the signal flowing through the wiring also has increased. As a result, when the crosstalk is calculated using the conventional method described above, even in a case where the crosstalk of 10% or less of the total number of wirings actually does not fall within the tolerable range, the check result obtained by the conventional method in an extreme case may indicate that the crosstalk of 50% or more of the total number of wirings does not fall within the tolerable range. When the check result is based on such an excessively strict checking, there is a problem in that the design efficiency of the wiring greatly deteriorates.
Such an excessively strict checking is made according to the conventional method because the peak value of the crosstalk noise is assumed to be simply proportional to the adjacent wiring length, even though the peak value of the crosstalk noise actually saturates and becomes approximately constant when a predetermined wiring length is exceeded as will be described later.